Utilizing advanced 3D modeling tools, an extensive database was established and used as an inseparable part of atmospheric composition studies. All investigations in this work were conducted with a high resolution, and up-to-date modeling tools was applied alongside with detailed and reliable input data. Employing the US Environmental Protection Agency (EPA) Model-3 system as a basic modelling tool, the models in it (WRF, CMAQ, and SMOKE) were adapted and validated specifically for Bulgaria. This framework gives the opportunity for better understanding of the present climate of atmospheric composition within the country and possibility for comprehensive examinations. On this basis are generate statistically significant ensemble of Air Quality Indexes (AQI), characterizing their typical recurrence, spatial distribution, and temporal variability across the country. Bulgaria, adopting the Bulgarian Chemical Weather Forecast System, operationally computes AQI. Ongoing numerical experiments, with a horizontal resolution of 1 km for Sofia, further the understanding of air quality dynamics in the city. An integral aspect of the AQ assessment involves the evaluation of AQ impact on human health and quality of life. Utilizing AQI as an integral characteristic of AQ provides a comprehensive assessment of pollutant impact, directly measuring air quality effects. All the AQI evaluations are based on air pollutants concentrations obtained from the numerical modelling and make it possible to reveal the AQI status. This paper's results enable the estimation of annual and seasonal recurrence patterns for the entire ensemble, and provide analyses of the potential causes for high values in different bands and different AQI statuses.